use crate::models::{budget_update::BudgetUpdate, category::Category};

use super::{calculate_budgets_accrual, find_by_id_or};

pub fn calculate_category_balance(
    category: &Category,
    transaction_sums: &[(i32, Option<i64>)],
    category_transfer_from_sums: &[(i32, Option<i64>)],
    category_transfer_to_sums: &[(i32, Option<i64>)],
    budget_updates: &[BudgetUpdate],
) -> i64 {
    let transaction_sum = find_by_id_or(transaction_sums, category.id, 0);
    let category_transfer_from_sum = find_by_id_or(category_transfer_from_sums, category.id, 0);
    let category_transfer_to_sum = find_by_id_or(category_transfer_to_sums, category.id, 0);
    let budget_accruals_sum = calculate_budgets_accrual(category, budget_updates);

    transaction_sum + budget_accruals_sum + category_transfer_to_sum - category_transfer_from_sum
}

#[cfg(test)]
mod test {
    use chrono::{Days, Utc};

    use crate::{
        models::{budget_update::BudgetUpdate, category::Category, date_time_utc::DateTimeUtc},
        utils::calculate_category_balance,
    };

    #[test]
    fn when_no_data_then_returns_zero() {
        let category = Category {
            id: 0,
            name: String::new(),
        };

        let result = calculate_category_balance(&category, &[], &[], &[], &[]);

        assert_eq!(result, 0_i64);
    }

    #[test]
    fn when_data_only_for_another_category_then_returns_zero() {
        let category = Category {
            id: 0,
            name: String::new(),
        };
        let transaction_sums = [(1, Some(100))];
        let category_transfer_from_sums = [(1, Some(91))];
        let category_transfer_to_sums = [(2, Some(79))];
        let budget_updates = [BudgetUpdate {
            id: 0,
            category_id: 1,
            date: DateTimeUtc::new(Utc::now().checked_sub_days(Days::new(120)).unwrap()),
            new_budget: 77,
            new_period: 1,
        }];

        let result = calculate_category_balance(
            &category,
            &transaction_sums,
            &category_transfer_from_sums,
            &category_transfer_to_sums,
            &budget_updates,
        );

        assert_eq!(result, 0_i64);
    }

    #[test]
    fn when_transaction_sum_is_none_then_returns_zero() {
        let category = Category {
            id: 0,
            name: String::new(),
        };
        let transaction_sums = [(0, None)];
        let category_transfer_from_sums = [];
        let category_transfer_to_sums = [];
        let budget_updates = [];

        let result = calculate_category_balance(
            &category,
            &transaction_sums,
            &category_transfer_from_sums,
            &category_transfer_to_sums,
            &budget_updates,
        );

        assert_eq!(result, 0_i64);
    }

    #[test]
    fn when_category_transfers_are_none_then_returns_zero() {
        let category = Category {
            id: 0,
            name: String::new(),
        };
        let transaction_sums = [];
        let category_transfer_from_sums = [(0, None)];
        let category_transfer_to_sums = [(0, None)];
        let budget_updates = [];

        let result = calculate_category_balance(
            &category,
            &transaction_sums,
            &category_transfer_from_sums,
            &category_transfer_to_sums,
            &budget_updates,
        );

        assert_eq!(result, 0_i64);
    }

    #[test]
    fn when_some_data_then_calculates_as_expected() {
        let category = Category {
            id: 0,
            name: String::new(),
        };
        let transaction_sums = [(0, Some(100))];
        let category_transfer_from_sums = [(0, Some(91))];
        let category_transfer_to_sums = [(0, Some(79))];
        let budget_updates = [BudgetUpdate {
            id: 0,
            category_id: 0,
            date: DateTimeUtc::new(Utc::now().checked_sub_days(Days::new(120)).unwrap()),
            new_budget: 77,
            new_period: 1,
        }];

        let result = calculate_category_balance(
            &category,
            &transaction_sums,
            &category_transfer_from_sums,
            &category_transfer_to_sums,
            &budget_updates,
        );

        let expected_result = 100 + (-91) + 79 + 77 * 120;
        assert_eq!(result, expected_result);
    }
}